The present invention relates to a recording material for ink jet printing and more particularly to a recording material which comprises a base material and a surface recording layer formed thereon and which is capable of allowing ink jet recording with the same dot size as on the conventionally employed non-sized paper and accordingly allowing perfect recording of solid images thereon even if printing is performed by an ink jet printing apparatus designed for use with such non-sized paper. The base material for this recording material is not limited to ink-absorbing materials, but it can be made of a material which does not absorb any liquid ink, such as a plastic film or plate, glass or ceramics.
Conventionally, the following recording sheets for ink jet printing are proposed: an ink jet recording sheet of a coated sheet type which comprises a sheet of plain paper and a recording layer formed thereon, which recording layer contains a polymeric binder agent or a pigment for increasing the density or resolution of the recorded images on the recording sheet (Japanese laid-open patent applications 57-93193 and 57-70691), and a non-porous recording material for ink jet printing, particularly for use with an overhead projector, which includes a surface layer containing a particular material which dissolves or swells in a liquid ink (Japanese laid-open patent application 56-80489).
Furthermore, for the purpose of increasing the water-resistance of the images recorded by ink jet printing on a recording medium, there is proposed in Japanese laid-open patent application 56-99636 an ink jet recording method of printing images on a recording medium containing a cationic surface active agent on the surface layer thereof by an aqueous ink containing at least a water-soluble direct dye or a water-soluble acidic dye.
Generally as the recording sheets for ink jet recording, non-sized sheets having high water absorbing capacity are employed. Accordingly the ink jet printing apparatus in general use is designed so as to yield an appropriate dot size when such non-sized sheets are employed. Therefore, when jet printing is performed on the above mentioned coated sheets and on the sheet for overhead projectors, an appropriate dot size cannot be obtained because of insufficient ink absorption of the ink and insufficient spreading of the printed dots on the sheets. The result is that perfect solid images cannot be formed, but non-printed areas are formed in the images to be solid. In particular, it is almost impossible to form perfect solid images on transparent sheets which are in general use for overhead projectors.